The importance of gas molecules in mammalian survival is exemplified by the requisite need for oxygen to sustain life. In 2000 the Noble Prize in Medicine was awarded for the discovery and characterization of nitric oxide (NO) as endothelial derived relaxation factor. This discovery revolutionized how we view gas molecules and spurned the activity of numerous laboratories to study the molecular mechanisms by which NO regulated and modulated cellular function, particularly in the cardiovascular arena. More recently in 1998, a second functional gas molecule was revealed; carbon monoxide, touted as a toxin to avoid, was shown to be a biologically active gas molecule with potent cytoprotective properties in vitro and in vivo at low concentrations. This discovery stemmed from work on the enzyme heme oxygenase-1, which is an inducible stress response gene that generates CO endogenously as it catabolizes heme in all cells. CO and NO have been well studied and continue to be evaluated from a mechanistic standpoint in numerous model systems. A great deal of information has been gleaned regarding the action of these gases related to signaling cascades and downstream gene regulation. CO unlike NO is non-reactive and acts on divalent cations such as iron contained in heme moieties of numerous enzymes to modulate their function. Whether CO binds to other metal cations is likely but has not yet been studied. Until the elucidation of these gases as biological mediators, gases have carried the dogma of simply being necessary to either fulfill metabolic requirements of the cell or as simple waste products of enzymatic processes. We believe there is a greater role for gases in overall cellular function and behavior and offer the innovative hypothesis that CO, which we will use as the prototype gas for our studies, functions as a gaseous transcriptional regulator operating as a homeostatic sensor within all cells at the level of DNA dynamics. We believe this fits the purpose of the EUREKA mechanism because it is a novel innovative and unconventional hypothesis which if proven to be valid will reshape current theory of DNA regulation, but also many aspects of cellular function and behavior including gene expression, but perhaps more importantly DNA damage and repair, as well as DNA synthesis and proliferation. Our central hypothesis is that gaseous CO interacts directly with DNA via metal ions in complex with polymerases and topoisomersases present on DNA. In the time allotted for this work we will evaluate the interaction of CO with DNA and how this influences transcription, recognition of damage and proliferation in the cell. We will test our hypothesis with the following aims: Specific Aim 1: To test the ability of CO to modulate DNA dynamics. Specific Aim 2: To evaluate the consequences of CO binding to DNA and/or polymerase to regulate transcription by fostering the unwinding of DNA and facilitating polymerase activity. Specific Aim 3: To evaluate the role of CO in DNA synthesis and the regulation of cellular proliferation.